1. Field of the Invention
This invention relates to refrigeration systems. More particularly, this invention relates to a refrigeration unit having a thermal storage control system that automatically adjusts the refrigeration unit set point within a cargo container that is loaded with refrigerated cargo, to utilize the frozen load of the cargo container itself to protect against drift above a set point during high ambient conditions or increased container heatleakage.
2. Description of the Prior Art
Thermal storage concepts have been widely used for hundreds of years. Conventional container refrigeration systems such as those using reciprocating compressor based systems, familiar to those skilled in the art of transport refrigeration, have generally been capable of holding deep frozen container temperatures (-20.degree. F. and below) when the ambient temperatures are below 80 to 85.degree. F. and the cargo containers are new with relatively low heat leakages. However, as cargo containers age, the container insulation degrades, making it increasingly more difficult to maintain the aforesaid deep frozen temperatures within these cargo containers to ensure the cargo being transported arrives at its destination without even minor impairment. In view of the above, attempts have been made by those skilled in the art of transport refrigeration to design and manufacture systems which utilize various refrigerants and/or compressor technologies.
Still needed, but not available with cargo container refrigeration systems presently known in the art is a refrigeration system that is capable of also reliably and efficiently establishing and maintaining precise deep frozen container temperature levels within a loaded cargo container, even during time periods when normal refrigeration system capacity is severely limited, such as when the cargo container insulation has deteriorated and/or ambient temperatures rise to levels that test the refrigeration capacity limits of the cargo container refrigeration unit.